package com.xt.purchasingsystem.utils;

import org.apache.poi.xssf.usermodel.*;

import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;

/**
 * 数据导出
 *
 * @param <T>
 */
public class ExportExcel<T> {

    public void exportExcel(String[] headers, Collection<T> dataset, String fileName, HttpServletResponse response) {
        // 声明一个工作薄
        XSSFWorkbook workbook = new XSSFWorkbook();
        // 生成一个表格
        XSSFSheet sheet = workbook.createSheet(fileName);
        // 设置表格默认列宽度为15个字节
        sheet.setDefaultColumnWidth((short) 20);
        // 产生表格标题行
        XSSFRow row = sheet.createRow(0);
        for (short i = 0; i < headers.length; i++) {
            XSSFCell cell = row.createCell(i);
            XSSFRichTextString text = new XSSFRichTextString(headers[i]);
            cell.setCellValue(text);
        }
        try {
            // 遍历集合数据，产生数据行
            Iterator<T> it = dataset.iterator();
            int index = 0;
            while (it.hasNext()) {
                index++;
                row = sheet.createRow(index);
                T t = (T) it.next();
                // 利用反射，根据javabean属性的先后顺序，动态调用getXxx()方法得到属性值
                Field[] fields = t.getClass().getDeclaredFields();
                for (short i = 0; i < headers.length; i++) {
                    XSSFCell cell = row.createCell(i);
                    Field field = fields[i+1];
                    String fieldName = field.getName();

                        String getMethodName = "get" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);
                        Class tCls = t.getClass();
                        Method getMethod = tCls.getMethod(getMethodName, new Class[]{});
                        Object value = getMethod.invoke(t, new Object[]{});
                        // 判断值的类型后进行强制类型转换
                        String textValue = null;
                        // 其它数据类型都当作字符串简单处理
                        if (value != null && value != "") {
                            textValue = value.toString();
                        }
                        if (textValue != null) {
                            XSSFRichTextString richString = new XSSFRichTextString(textValue);
                            cell.setCellValue(richString);
                        }

                }
            }
            getExportedFile(workbook, fileName, response);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //产生输出
    public void getExportedFile(XSSFWorkbook workbook, String name, HttpServletResponse response) throws Exception {
        BufferedOutputStream fos = null;
        try {
            String fileName = name + ".xlsx";
            response.setContentType("application/x-msdownload");
            response.setHeader("Content-Disposition", "attachment;filename=" + new String(fileName.getBytes("gb2312"), "ISO8859-1"));
            fos = new BufferedOutputStream(response.getOutputStream());
            workbook.write(fos);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                fos.close();
            }
        }
    }

}
